Investments - Summary of Other Equity Investments (Details) - Other Equity Method Investments [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 86,867	$ 79,717
G5 Evercore [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	27,060	26,016
ABS [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	39,850	38,982
Atalanta Sosnoff [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	14,457	14,719
Luminis [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 5,500	$ 0